The present invention relates to machines for making ice-cream and similar cold products. In particular, it concerns a machine of the type having a freezing container which is insertable in and removable from a cooling chamber comprising a substantially cylindrical cooling coil of the type constituted by a plurality of lengths of tubing connected together in series by means of two manifold bodies which are spaced apart in a circumferential direction and define a passage. A substantially cylindrical elastic sheath which has a discontinuity along a generatrix in correspondence with the passage surrounds the coil, and a layer of elastically yielding thermally insulating material is interposed between the coil and the sheath.
As is known, in a machine for making ice-cream, the ability to remove the freezing container enables several important advantages to be obtained. In particular, it facilitates the rapid recovery of the ice-cream product by simply overturning the removed container, makes cleaning operations easier and more efficient, and permits successive production cycles with greatly reduced down times.
However, it is also known that the removability of the freezing container creates problems which are difficult to solve, primarily the thermal efficiency.
Machines have been proposed, for example, in which the freezing container is immersed in a brine of water, ice and salt, which in turn is contained in a container cooled by a coil. However, this technique is known to involve serious complications in construction, as well as great inconvenience in use.
Another type of machine proposed is that in which the freezing container is conical and can be inserted into a corresponding conical basket formed by the coil. The thermal efficiency is so low, however, due to the uncertain contact between the coil and the freezing container, that any practical embodiment has proved unsatisfactory.
A third type of machine is described in the co-pending U.S. Application Ser. No. 574,593 filed on Jan. 27, 1984 by the same Applicant and now U.S. Pat. No. 4,538,427. In a machine of this type, the freezing container is insertable in and removable from a cylindrical cooling chamber comprising two half-shells which can be opened to receive the container and can be closed around it. The cooling coil which forms the chamber is elastically yielding in a radial direction relative to the chamber. This solution is undoubtedly a considerable advance over the prior art, enabling better contact between the cooling coil and the freezing container with greater efficiency of the machine.
The efficiency is further improved in a machine of the type described in the co-pending U.S. Application Ser. No. 610,766, filed on May 16, 1984 by the same Applicant and now U.S. Pat. No. 4,535,604. In this machine, the cylindrical cooling chamber has a circular cross-section which is not completely closed on itself due to the presence of a slit extending along a generatrix. The side of the chamber comprises an elastic outer sheath, and means are provided for enlarging the chamber by opening the slit against resilient means constituted by the sheath. In this machine the contact between the cooling coil and the freezing container is further improved, and, with it, the efficiency is improved.
Like these ice-cream-making machines, the present invention tackles the problem of further improving the already good thermal efficiency.